A vibration motor (or a vibration actuator) is that which communicates, to a user of a communication device or to an operator who is holding any of a variety of electronic devices, the state of an input signal through a vibration, through generating a vibration through an incoming call on a communication device or through the transmission of an alarm on any of a variety of electronic devices, and is built into any of a variety of electronic devices, such as mobile information terminals, including mobile telephones.
Among the various types of vibration motors under development, there is a known linear vibration motor that is able to generate relatively large vibrations through linearly reciprocating vibrations. This linear vibration motor employs a structure that is provided with a straight stationary shaft, and a needle is vibrated therealong, making it possible to achieve stabilized vibration with little noise produced by components striking each other, and making it possible to achieve resistance to damage, such as when there is a drop impact, through the needle being held by the stationary shaft.
In the prior art for linear vibration motors that are equipped with stationary shafts there have been proposals for those wherein a driving portion is structured from a coil that is secured to a case and a magnet that is disposed within the coil, a needle is structured through connecting a weight portion to the magnet along the direction of vibration, a through hole is formed in the needle along the direction of vibration, and a single stationary shaft is passed through this through hole (See, for example, Japanese Unexamined Patent Application Publication No. 2012-16153), or two stationary shafts are provided along the direction of vibration, a driving portion made from a coil and a magnet is disposed between the two stationary shafts, and a needle that is provided with a weight portion and which is driven by the driving portion is supported by the two stationary shafts so as to be able to slide (See, for example, Japanese Unexamined Patent Application Publication No. 2011-97747), and the like. In each of these prior art technologies, coil springs are provided around the stationary shaft, and the needle is caused to undergo reciprocating vibration along the stationary shaft through the driving force by the driving portion in one direction and the elastic force of the coil spring in opposition to the driving force.